Bottom Line:
We studied Mycobacterium avium lymphadenopathy in 183 Swedish children (<7 years of age) from 1998 through 2003.Seasonal variation in the frequency of the disease, with a peak in October and a low point in April, suggests cyclic environmental factors.We also found a higher incidence of the disease in children who live close to water.

ABSTRACTWe studied Mycobacterium avium lymphadenopathy in 183 Swedish children (<7 years of age) from 1998 through 2003. Seasonal variation in the frequency of the disease, with a peak in October and a low point in April, suggests cyclic environmental factors. We also found a higher incidence of the disease in children who live close to water.

Figure 1: Seasonal incidence of Mycobacterium avium infection in Swedish children (1983–2003) in our study (bars = real numbers) and as predicted by nonlinear regression sine functions (equations: y = a + bsin[(x – c)Π/6], where x represents the months (1–12) (www.smhi.se), and with “a,” “b,” and “c” characteristic for each curve and b ≠ 0 with statistical significance, p<0.05, for all these curves. (See also online Appendix Table, available from www.cdc.gov/EID/content/14/4/661-appT.htm) A) All children. The curves were statistically significant, p<0.05, for both 1983–1997 and 1998–2003, and so the data for all years were grouped together. UCL, upper confidence limit; LCL, lower confidence limit. B) Children <2 years and >2 years of age, respectively. “b,” amplitude of curve, has a tendency to be greater for children <2 years of age (p = 0.07) and “c” is slightly smaller for children >2 years of age, representing a shift to the right of the curve, though not statistically significant. Pred, predicted.

Mentions:
Incidence rates were calculated and the corresponding 95% confidence intervals estimated by using the Poisson distribution, since events that occur randomly in time follow this distribution. Results of seasonal variations were tested with a commercial statistical software (Statistica version 7.1; Statsoft, Tulsa, OK, USA), by using nonlinear regression fitting a sine function (Figure 1).We considered p values <0.05 statistically significant. (See also online Appendix Table, available from www.cdc.gov/EID/content/14/4/661-appT.htm)

Figure 1: Seasonal incidence of Mycobacterium avium infection in Swedish children (1983–2003) in our study (bars = real numbers) and as predicted by nonlinear regression sine functions (equations: y = a + bsin[(x – c)Π/6], where x represents the months (1–12) (www.smhi.se), and with “a,” “b,” and “c” characteristic for each curve and b ≠ 0 with statistical significance, p<0.05, for all these curves. (See also online Appendix Table, available from www.cdc.gov/EID/content/14/4/661-appT.htm) A) All children. The curves were statistically significant, p<0.05, for both 1983–1997 and 1998–2003, and so the data for all years were grouped together. UCL, upper confidence limit; LCL, lower confidence limit. B) Children <2 years and >2 years of age, respectively. “b,” amplitude of curve, has a tendency to be greater for children <2 years of age (p = 0.07) and “c” is slightly smaller for children >2 years of age, representing a shift to the right of the curve, though not statistically significant. Pred, predicted.

Mentions:
Incidence rates were calculated and the corresponding 95% confidence intervals estimated by using the Poisson distribution, since events that occur randomly in time follow this distribution. Results of seasonal variations were tested with a commercial statistical software (Statistica version 7.1; Statsoft, Tulsa, OK, USA), by using nonlinear regression fitting a sine function (Figure 1).We considered p values <0.05 statistically significant. (See also online Appendix Table, available from www.cdc.gov/EID/content/14/4/661-appT.htm)

Bottom Line:
We studied Mycobacterium avium lymphadenopathy in 183 Swedish children (<7 years of age) from 1998 through 2003.Seasonal variation in the frequency of the disease, with a peak in October and a low point in April, suggests cyclic environmental factors.We also found a higher incidence of the disease in children who live close to water.

ABSTRACTWe studied Mycobacterium avium lymphadenopathy in 183 Swedish children (<7 years of age) from 1998 through 2003. Seasonal variation in the frequency of the disease, with a peak in October and a low point in April, suggests cyclic environmental factors. We also found a higher incidence of the disease in children who live close to water.